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When 0.936 g of calcium chloride (CaCl2) is dissolved in 114 g of water, the temperature increases from 25.00°C to 26.52°C. Calculate q for the water and ΔH° for the process, assuming that the heat absorbed by the salt is negligible.

Options:
a) q = 48.5 kJ, ΔH° = 48.5 kJ
b) q = 23.2 kJ, ΔH° = 23.2 kJ
c) q = 14.8 kJ, ΔH° = 14.8 kJ
d) q = 31.7 kJ, ΔH° = 31.7 kJ

1 Answer

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Final answer:

By using the formula q = mcΔT, the heat absorbed by the water when calcium chloride is dissolved is found to be 0.7252 kJ. The enthalpy change (ΔH°) for the process can be calculated with the molar heat of solution for calcium chloride and the number of moles dissolved, resulting in approximately +0.6989 kJ.

Step-by-step explanation:

To calculate the heat (q) absorbed by the water when calcium chloride (CaCl2) is dissolved, we can use the formula q = mcΔT, where m is the mass of the water, c is the specific heat capacity of water (4.184 J/g°C), and ΔT is the change in temperature. The mass of the water is given as 114 g, and the temperature increase is 1.52°C (from 25.00°C to 26.52°C). Plugging these numbers into the equation, we get q = 114 g x 4.184 J/g°C x 1.52°C which equals approximately 725.2 joules or 0.7252 kJ for the water.

To find the ΔH° for the process, we can look at the molar heat of solution for calcium chloride which is given as -82.8 kJ/mol. Since we have 0.936 g of CaCl2, we can convert this to moles using its molar mass (110.98 g/mol for CaCl2), which gives us approximately 0.00843 mol. Multiplying the molar heat of solution by the number of moles gives the ΔH° for the process as -0.00843 mol x -82.8 kJ/mol which equals approximately +0.6989 kJ.

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